The present invention relates to tools for setting fasteners having pin members with pull grooves and more particularly to tools having a plurality of jaws for gripping the pull grooves.
In the setting of multi-pieced fasteners generally of types such as those shown in the U.S. Pat. Nos. 2,527,307 and 2,531,048 issued to L. C. Huck on Oct. 24, 1950 and Nov. 21, 1950, respectively, it has been the practice to utilize a tool having a plurality of generally independently movable chuck jaws. The latter are generally shown in the above noted patents to L. C. Huck and the details of the same are exemplified in the U.S. Pat. No. 3,107,806 issued Oct. 22, 1963 to G. J. Van Hecke et al.
With such jaw structures it is possible under certain conditions of pin insertion to move the jaws out of axial alignment. When this occurs and the tool is actuated, the pin is gripped by less than the full complement of jaws; this can lead to stripping of the jaw teeth, stripping of the pull grooves and/or ultimate failure of one or more jaws.
In addition such jaw structures are normally held closed by a spring biased jaw follower assembly. Thus, in order to insert the pin into the jaws the spring bias load must be overcome as the jaws are moved axially rearwardly and radially outwardly. In some assembly operations such insertion loads can be undesirably high.
For example, the insertion load magnitude appears to be aggravated by fasteners in which the grooves to be gripped on the pin are relatively deep. Such a fastener structure is shown and described in copending patent application Ser. No. 899,591, filed Apr. 24, 1978 and which issued into U.S. Pat. No. 4,208,943 on June 24, 1980; the disclosure of the latter patent application is fully incorporated herein by reference. With such fasteners it is possible for one of the jaws to be permanently moved from its proper position requiring the tool to be disassembled and the jaw properly positioned again. In addition, occasionally with the latter type fastener, pin break may occur across more than one groove resulting in relatively small sized debris being carried into the tool. With conventional tool structures, the large number of relatively independently movable parts provides an environment in which the debris may lodge and eventually jam the tool or seriously impair its operation. As shown in the above noted copending application the fastener includes a pin member having a plurality of grooves and associated crests; these grooves and crests are substantially identical annular combination locking and breakneck grooves defined by cooperating side walls which converge into a selected concave radius portion. This concave radius portion is of a magnitude selected to provide a predetermined stress concentration to facilitate fracture at a selected one of the grooves proximate the outer end of an associated collar.
In the present invention the jaws, which are conventionally constructed of hardened steel, are secured to an elastomeric structure such that the axial misalignment is substantially precluded. At the same time the jaws are held in a preselected open position whereby insertion loads are minimized. Since the number of parts is substantially reduced the likelihood of the tool jamming from debris is minimized.
Thus the tool and the noted fastener cooperate to provide a novel fastening system. It should be noted, however, that the tool can be utilized with fasteners of a different construction.